Rotman lens-based two-tier hybrid beamforming for wideband mmWave MIMO-OFDM system with beam squint

EURASIP Journal on Wireless Communications and Networking

Bin Liu¹  Hongbo Zhu¹ 

[1] Jiangsu Key Laboratory of Wireless Communications, Nanjing University of Posts and Telecommunications;

关键词: Hybrid precoding;    Millimeter wave;    Wideband system;    MIMO;    Beam squint;    Multiuser interference;   

DOI  :  10.1186/s13638-018-1280-5

来源: DOAJ

【 摘 要 】

Abstract In this paper, we study the hybrid beamforming for the wideband mmWave multiuser MIMO-OFDM system. We characterize the frequency-dependent beam angle problem, i.e., beam squint effect. Firstly, we extend the mmWave channel model from the Saleh-Valenzuela representation with the consideration of beam squint. Secondly, a two-tier hybrid beamforming is proposed to achieve the maximum spectral efficiency in wideband mmWave multiuser MIMO-OFDM system. In the first tier, the Rotman lens array is adopted as the analog precoder to provide true-time-delay (TTD) and reduce the beam squint impairment. Moreover, the first-tier baseband precoder is designed based on block diagonalization (BD) to cancel inter-user interference. We further consider the finite spatial resolution and power leakage problem of the lens array. The second-tier hybrid precoder is proposed to collect the leak power with the phase shifter array. The optimal second-tier hybrid precoder design is formulated as the matrix factorization problem, and the two-tier hybrid precoding algorithm is based on the alternative minimization. It is found that both the beam squint and frequency-selective effect should be considered in the wideband mmWave system. Simulation results show that the proposed two-tier hybrid precoder could reduce beam squint impairment and inter-user interference, and could approximate to the optimal full-digital precoder with much fewer RF chains.

【 授权许可】

Unknown